Private relays make it possible to de-couple the data layer from the interface for private apps
Example: if you use bitwarden, you are stuck with the bitwarden API, but maybe you like the lastpass interface better
But if your passwords are stored on your private relay, you can swap between any interface you like without having to do imports/exports and installing new things
Basically static, app specific APIs can become obsolete with a good set of NIPs
Not only that, but all the generic meta-nips automatically apply to all new kinds. For example, you can register a nip 89 handler for anything, or advertise relay support for any kind. Kinds are so awesome.
💯 but don’t forget to fuck your wife before someone else do, like always
Only in sense of exchanging data. the protocol. The app needs to undrestand data structures to operate.
Like curl can deal with http or dig with dns records. It doesn't know what to do with the data.
Frankly, I don't understand why I should choose nostr protocol instead of say dns (it's binary, fast, can hold arbitrary data and supports queries).
Check out WebIndexP2P which does exactly that. Fine tuned private nostr relays would be very similar to wip2p nodes.